Add gem push submodule to Makefile

[wshayes]

Add gem push submodules. Currently only pushing openbel-api gem when running make deploy-{major|minor|patch}.

[abargnesi]

To do this right we should delegate the build and push tasks to the submodules. This will be important for bel_parser, bel-search-sqlite, and bel-rdf-jena projects that build for specific rubies.

Additionally the build steps should run tests and only trigger release if all pass.

I'll take a look this weekend.